A predominant number of color picture tubes in use today have line screens and shadow masks that include slit-shaped apertures. The apertures are aligned in columns, and the adjacent apertures in each column are separated from each other by webs or tie bars in the mask. Such tie bars are essential in the mask to maintain its integrity when it is formed into a dome-shaped contour which somewhat parallels the contour of the interior of a viewing faceplate of a tube. Tie bars in one column are offset in the longitudinal direction of the column (vertical direction) from the tie bars in the immediately adjacent columns.
When a mask is formed into a dome-shaped contour, the forming process stretches the tie bars in the mask. Such stretching is nonuniform throughout the mask because the forces on the mask during forming are nonuniform throughout the mask. This stretching of the webs has an adverse effect on the mask, in that the slit apertures in the mask are stretched beyond their desired sizes. Furthermore, sometimes when the mask is formed into its dome-shape, the tie bars tear, thus ruining the mask. Therefore, there is a need for some solution to the problem of tie bar stretching.